A surgical stapling head assembly is the medical instrument used for performing a circular anastomosis stapling operation, which can be operated easily and the surgery operation time can be effectively reduced. The surgical stapling head assembly has distinct advantages over the manual suture, which is approved by more and more doctors and patients. A circular stapling instrument is used for performing a circular anastomosis stapling operation, unwanted tissues are cut while suturing, however, the annular cutter of prior art works in way of straight forward and straight backward thereby the doctor has to exert large force when doing the operation so that tissues are able to be cut by impulsive force, sometimes the tissues may not be cut completely and the uncut tissues will be stretched to break by the force from the stapling instrument while retreating, which brings tensile damages to anastomosis ring and the result is serious. To overcome the defects as mentioned above, rotary cutting instrument is invented by changing the straight cutting of prior art into rotary cutting, the cutting effects are greatly improved and the doctors can exert much less force when doing operations.
However, tracks for rotary cutting have comparatively monotonous function, the same helix tracks function not only as forward tracks but also function as backward tracks, the annular cutter has to rotate to retreat and it suffers comparatively large resistance because the backward journey is comparatively long. Furthermore, the rotary cutter of prior art is enabled by disposing ball device between the annular cutter and staple driver, the rotary cutter is connected with the staple driver by means of two slender catches, when the annular cutter is pressed tightly with the staple driver by the catches, the annular cutter will be subject to large friction resistance; when the annular cutter is pressed loosely with the staple driver by the catches, due to influences from self gravity and other factors, the annular cutter may deviate from central axis slightly when cutting tissues, therefore, the shape of the cut is not a full circle, there is a potential danger of cutter being stuck and unmovable when the annular cutter deviates too much from the central axis, which may affect the implementation of the surgery operations.